和正八面體OHP投影類似，二十面體投影(ISP，Icosahedron projection format)采用二十面體作為投影模型。ISP也支援緊湊型和非緊湊型兩種展開方式，圖1中左側為緊湊型，右側為非緊湊型。
圖1 ISP投影
ISP的二十面體有12個角和20個面，表1是ISP中個角在XYZ坐标系中的定義，表2是各面的定義。
表1 ISP中角的定義
| 角 | 非緊湊型 | 緊湊型 |
| V0 | (1,c,0) | (0,1.902,0) |
| V1 | (-1,c,0) | (0.526,0.851,1.618) |
| V2 | (1,-c,0) | (−0.526,−0.851, −1.618) |
| V3 | (-1,-c,0) | (0,−1.902, 0) |
| V4 | (0,1,c) | (1.701,0.851, 0) |
| V5 | (0,-1,c) | (1.376,−0.851, −1) |
| V6 | (0,1,-c) | (−1.376,0.851, 1) |
| V7 | (0,-1,-c) | (−1.701,−0.851, 0) |
| V8 | (c,0,1) | (0.526,0.851, −1.618) |
| V9 | (c,0,-1) | (−1.376,0.851, −1) |
| V10 | (-c,0,1) | (1.376,−0.851, 1) |
| V11 | (-c,0,-1) | (−0.526,0.851, 1.618) |
其中
表2 ISP中面的定義
| 面的索引 | 非緊湊型 | 緊湊型 |
| {V0,V8, V9} | {V8,V9, V0} | |
| 1 | {V2,V9, V8} | {V2,V9, V8} |
| 2 | {V0,V9, V6} | {V0,V9, V6} |
| 3 | {V7,V6, V9} | {V7,V6, V9} |
| 4 | {V0,V6, V1} | {V6,V1, V0} |
| 5 | {V11,V1, V6} | {V11,V1, V6} |
| 6 | {V0,V1, V4} | {V4,V0, V1} |
| 7 | {V10,V4, V1} | {V10,V4, V1} |
| 8 | {V0,V4, V8} | {V0,V4, V8} |
| 9 | {V5,V8, V4} | {V5,V8, V4} |
| 10 | {V3,V10, V11} | {V3,V10, V11} |
| 11 | {V1,V11, V10} | {V1,V11, V10} |
| 12 | {V3,V5, V10} | {V10,V3, V5} |
| 13 | {V4,V10, V5} | {V4,V10, V5} |
| 14 | {V3,V2, V5} | {V2,V5, V3} |
| 15 | {V8,V5, V2} | {V8,V5, V2} |
| 16 | {V8,V5, V2} | {V3,V7, V2} |
| 17 | {V9,V2, V7} | {V9,V2, V7} |
| 18 | {V3,V11, V7} | {V11,V7, V3} |
| 19 | {V6,V7, V11} | {V6,V7, V11} |
Frame Packing
ISP支援兩種frame packing方式：緊湊型和非緊湊型。
圖2 ISP frame packing方式